1. Field of the Invention
The present invention relates generally to a method of controlling a washing machine, and more particularly to a method of controlling a washing machine, which can wash laundry by causing a washboard installed on the inner surface of the bottom of a spin-drying tub to wobble.
2. Description of the Related Art
Generally, washing machines are devices for washing laundry by rotating a cylindrical rotating tub in which laundry and washing water are contained. Such washing machines are classified into two types: a drum type in which a rotating tub is horizontally arranged to wash laundry by upwardly raising laundry along the inner circumferential surface of the rotating tub and dropping the laundry while the rotating tub rotates in a normal direction or a reverse direction around a horizontal shaft, and a vertical shaft type in which a spin-drying tub having a pulsator formed therein is vertically arranged to wash laundry by using a water stream generated by the pulsator while the spin-drying tub rotates in a normal direction or a reverse direction around a vertical shaft.
FIG. 1 is a view showing the construction of a conventional vertical shaft washing machine having a pulsator to wash laundry. As shown in FIG. 1, the conventional vertical shaft washing machine having a pulsator comprises a housing 1 to form an external shape of the washing machine, a cylindrical washing tub 2 vertically arranged within the housing 1 to contain washing water therein, a cylindrical spin-drying tub 3 rotatably arranged within the cylindrical washing tub 2 and provided with a plurality of perforation holes 3c formed in an outer surface of the cylindrical spin-drying tub 3, a pulsator 4 installed in a lower portion of the cylindrical spin-drying tub 3 to generate a washing water stream, and a reversible drive motor 5 and a power transmission device 6 which are installed beneath the cylindrical washing tub 2 to selectively rotate the pulsator 4 and the cylindrical spin-drying tub 3.
The housing 1 is opened at a top of the housing 1 to allow a user to put laundry in the cylindrical spin-drying tub 3 or take out the laundry from the cylindrical spin-drying tub 3; A door 7 is hingedly attached to the opened top of the housing 1 to selectively open and shut the cylindrical spin-drying tub 3. Further, a drain hose 8 extended to an outside of the housing 1 is connected to a bottom of the cylindrical washing tub 2 so as to drain the washing water contained in the cylindrical washing tub 2 to the outside when a washing operation is completed.
A spin-drying shaft support 9 is installed beneath the bottom 3a of the cylindrical spin-drying tub 3 to couple a spin-drying shaft 6a of the power transmission device 6 with the cylindrical spin-drying tub 3, thus allowing the cylindrical spin-drying tub 3 to rotate according to the rotation of the spin-drying shaft 6a in a spin-drying process. Further, a washing shaft 6b of the power transmission device 6, which is installed to penetrate through the spin-drying shaft 6a, is coupled to the pulsator 4 arranged on the bottom of the cylindrical spin-drying tub 3 to rotate the pulsator 4 by rotating the washing shaft 6b in a washing process.
In the convention vertical shaft washing machine having the pulsator 4 constructed as described above, when the washing machine is operated after laundry is put in the cylindrical spin-drying tub 3, water is supplied to the cylindrical washing tub 2, and the pulsator 4 is alternately rotated in the normal direction and the reverse direction by the rotation of the reversible drive motor 5 and the washing shaft 6b of the power transmission device 6. Due to the rotation of the pulsator 4 in the normal direction and the reverse direction, a washing water stream is generated in the normal direction and the reverse direction, so laundry rubs against a surface of the cylindrical spin-drying tub 3 while being moved together with the washing water stream, thereby allowing laundry to be washed.
After a predetermined period of time elapses and a washing process is completed, a rinsing process of draining the washing water through the drain hose 8 and removing detergent from the laundry is carried out. Then, the cylindrical spin-drying tub 3 is rotated in one direction at a high speed by a rotation of the reversible drive motor 5 and the spin-drying shaft 6a of the power transmission device 6 to dry the laundry, thus completing the washing of the laundry.
However, the conventional vertical shaft washing machine operated as described above washes laundry using washing water streams generated by alternate rotation of the pulsator in the normal and in the reverse directions. Accordingly, laundry is moved alternately in the normal and reverse directions, so the laundry can become twisted and entangled. Consequently, the conventional vertical shaft washing machine is problematic in that laundry is easily worn out or damaged, and the user experiences inconvenience and can waste time untangling the laundry when the washing of the laundry is completed.
Meanwhile, the conventional washing machine using the pulsator is problematic in that the conventional washing machine operates by alternately rotating the pulsator in the normal and the reverse directions at short time intervals in the washing process, thus increasing power consumption due to alternate activations of the motor in both directions, which shortening the life span of the motor due to the above described operations.
Further, the conventional washing machine using the pulsator must fill the washing tub with a relatively large amount of the washing water so as to wash the laundry by agitating the laundry left and right by the washing water stream. Therefore, the amount of water used is increased, and the amount of detergent used is inevitably increased due to the increase of the amount of water used. Accordingly, the conventional washing machine is problematic in that the conventional washing machine causes an excessive waste of the wash water, which causes environmental pollution due to the increase of the amount of detergent used. According to recent trends to saving water and tightening restrictions against environmental pollution, the above disadvantages of the conventional washing machine are problems, which urgently must be solved.
In consideration of these problems, there recently was proposed a method of washing laundry by applying mechanical impacts to the laundry using a wobbling device, which can relieve the above problems.
However, the above-described method using a wobbling device also requires a control method increasing cleaning performance in proportion to the reduction of the amounts of both washing water and detergent used, and preventing the entanglement of laundry. Further, if a user does not immediately take out laundry from the washing tub after a spin-drying process is completed, the entangled laundry becomes stiffened. Therefore, a method is required to loosen the laundry to allow the user to later easily take out the laundry, and minimizing the generation of wrinkles of the laundry.